Plasma ethching apparatus and plasma etching process

ABSTRACT

A plasma etching apparatus includes: a chamber capable of reducing pressure; a substrate support provided inside the chamber to place a substrate; a first electrode which is arranged outside and in proximity to the chamber and to which high frequency power is applied to generate plasma of an etching gas in the chamber; and a second electrode comprising a plurality of separated electrodes which are arranged between the chamber and the first electrode and to each of which high frequency power is applied independently.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2004-066692 filed in Japan on Mar. 10,2004, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a plasma etching apparatus and a plasmaetching process mainly used for patterning an electrode material film ofa ferroelectric capacitor. In particular, the invention relates to aplasma etching apparatus for fine patterning of the electrode materialfilm while suppressing particle generation and a plasma etching processusing the same.

(b) Description of Related Art

With the increase in density, functionality and speed of semiconductorintegrated circuit devices in recent years, techniques of using anonvolatile memory (e.g., FeRAM (Ferroelectric Random Access Memory))have been proposed. In the nonvolatile memory, a ferroelectric film suchas of SBT (strontium bismuth tantalate) or PZT (lead zirconic titanate)is used for a capacitor insulating film. Further, a simple substancefilm such as of platinum (Pt) or iridium (Ir) is used as a capacitorelectrode material and a plasma dry etching technique mainly with achlorine gas is employed for fine patterning thereof. However, it isextremely difficult to dry etch these electrode material films. Thereason therefor is explained below.

Table 1 shows etching reaction products generated through a reactionbetween various kinds of electrode material films and achlorine-containing etching gas, together with their boiling points.TABLE 1 Substance Boiling point PtCl₂ 581° C. PtCl₄ 370° C. IrCl₃ 763°C. SiCl₄  58° C.

As shown in Table 1, if the electrode material film is a polysiliconfilm which is used for a general integrated circuit, SiCl₄ is generatedas an etching reaction product. Since SiCl₄ has a boiling point as lowas about 58° C., the product is easily gasified in an etching reactionchamber and emitted outside.

On the other hand, PtCl₂, PtCl₄ and IrCl₃, which are products generatedby a reaction between Pt or Ir and the chlorine-containing etching gas,have remarkably high boiling points as compared with SiCl₄, andtherefore these products are hard to gasify (vaporize). Accordingly,these reaction products do not go out of the chamber during the etchingand remain adhered to the chamber wall. This will be a cause of particlegeneration in the later step. Especially in a plasma etching apparatus,a top plate of the chamber is generally opposed to a semiconductor waferto be etched. Therefore, the reaction product adhered to the top platemay drop in the form of particles onto the wafer during the etchingprocess to cause a defect in the fine pattern. This is a serious problemin manufacturing the semiconductor integrated circuits.

Among commonly used inductively coupled dry etching apparatuses, thereis an apparatus comprising a Faraday shield electrode (hereinafterreferred to as an FS electrode) arranged between the outer wall of thechamber and an inductively coupled coil (hereinafter referred to as anICP coil) arranged to surround the outer wall to generate plasma of anetching gas in the chamber. In this apparatus, a voltage or highfrequency power is applied to the FS electrode to prevent an insulatingmaterial forming the inner wall of the chamber from being etched by theplasma (for example, see Japanese Unexamined Patent Publication No. HEI10-275694).

FIG. 5A shows a schematic configuration of an inductively coupled plasmatreatment apparatus (etching apparatus) provided with a conventional FSelectrode. As shown in FIG. 5A, an electrode 2 serving also as a wafersupport is arranged inside a chamber 1 for performing plasma treatmentsuch as dry etching. The electrode 2 is installed on the bottom of thechamber 1 via a support member 2 a and a wafer 3 to be plasma-treated isplaced on the electrode 2. Further, a high frequency bias voltage isapplied to the electrode 2 from a high frequency power source 4.

At the top of the chamber 1, a top plate 7 made of quartz or ceramic isarranged to be opposed to the electrode 2 or the wafer 3. An inductivelycoupled coil 5 (hereinafter referred to as an ICP coil 5) for generatingplasma in the chamber 1 is provided in proximity to the top surface ofthe top plate 7, i.e., the outer wall of the chamber 1. A high frequencyvoltage is supplied to the ICP coil 5 from a high frequency power source6. Further, an FS electrode 40 having the aforesaid function is insertedbetween the ICP coil 5 and the top plate 7.

During the etching of the wafer 3, a suitably adjusted high frequencyvoltage is applied to the FS electrode 40 from a high frequency powersource 10, which prevents the insulating material, especially formingthe top plate 7, from being etched by plasma ion impact.

FIG. 5B is a plan view of the FS electrode 40 of the etching apparatusshown in FIG. 5A. In general, the FS electrode 40 is circular whenviewed in plan as shown in FIG. 5B and is plate-shaped when viewed insection as shown in FIG. 5A.

The etching apparatus of FIG. 5A has an exhaust port 13 at the bottomthereof. Releasing a gate valve 12 brings a pressure-reduced state (astate where the pressure is lower than normal (atmospheric) pressure) inthe chamber 1.

In contrast to the apparatus of FIG. 5A, in an apparatus not having theFS electrode, i.e., the Faraday shield, the generated plasma and theinductively coupled coil are coupled not only inductively but alsocapacitively. Accordingly, the insulating material such as quartzserving as the chamber wall is etched by the plasma. Especially in thevicinity of the inner wall of the chamber immediately below the ICPcoil, electrons and ions in the plasma are accelerated in the directionvertical to the chamber inner wall by the high voltage applied to thecoil at high frequency. Since the mass of the electrons is far smallerthan that of the ions, the chamber inner wall is collided with theelectrons more predominantly than the ions and thereby to be negativelycharged. As a result, the ions carrying the opposite charge areattracted to the negatively charged area and the chamber wall materialis etched by the ion impact.

On the other hand, in the etching apparatus configured as shown in FIG.5A, the FS electrode 40 is provided between the ICP coil 5 and theinsulating material for the inner wall of the chamber 1 and a voltage isapplied to the FS electrode 40, thereby preventing the chamber wall frombeing etched. The FS electrode 40 is provided essentially for preventingthe chamber inner wall from being wasted by the etching. If the voltageapplied to the FS electrode 40 is optimized, an optimum capacitivecoupling component is surely obtained at the area in the chamber 1 madeof the insulating material and immediately below the ICP coil 5. In thiscase, a reaction product generated during the etching and adhered to thechamber inner wall can be etched by making use of a self-bias voltagedue to the capacitive coupling component. That is, in theabove-mentioned ideal case, the etching apparatus of FIG. 5A allowsetching, while preventing the insulating material forming the chamberinner wall from being etched and controlling the adhesion of thereaction product generated during the plasma etching to some extent(i.e., reducing the generation of particles).

BRIEF SUMMARY OF THE INVENTION

In a fine ferroelectric nonvolatile memory in which the minimum designsize for the circuit is generally 0.18 μm or smaller, however, a film oflayered structure made of conductive materials containing Pt, Ir or bothof them has come to be used as the capacitor electrode material film.Accordingly, a mixture such as PtCl₄ or IrCl₃ is generated as thereaction product during the etching of the multilayered film. Therefore,the reaction product is more prone to remain in the chamber as comparedwith the case of etching the electrode film made of a single material,which is employed for a capacitor of a memory with a relatively largerpattern size. In the apparatus of FIG. 5A, the reaction product adheresto the surface of the top plate 7 serving as the chamber inner wall.Furthermore, the reaction product is apt to adhere in larger thicknessto a center part of the top plate 7 than to other parts. The reasontherefor is considered as follows. Due to the relative arrangement ofthe wafer 3 and the top plate 7 where the surface of the wafer 3 isopposed to the center part of the top plate 7 as shown in FIG. 5A, thedistance between the surface of the wafer 3 and the center part of thetop plate 7 is the smallest and the distance between the surface of thewafer 3 and the periphery of the top plate 7 is relatively large.Accordingly, the reaction product released from the wafer surfacethrough the etching reaches the center part of the top plate 7 with moreease.

As described above, if the reaction product adhered to the chamber innerwall has a nonuniform thickness distribution (unevenness), the reactionproduct may possibly remain in the center part of the top plate 7 evenif optimization is given to the voltage value applied to the FSelectrode 40, i.e., the bias voltage component applied to the insulatingchamber inner wall such as the top plate 7 immediately below the ICPcoil 5 (and induced by the capacitive coupling). Where the reactionproduct remains adhered to the insulating chamber inner wall in thisway, there is caused a problem in that particles are generated insidethe chamber 1 and fall onto the wafer 3 to cause defects.

Further, in the conventional etching apparatus shown in FIG. 5A, thedegree of adhesion of the reaction product is not specified by in-situobservation. In other words, it is unclear where and to what extent thereaction product actually adheres. Therefore, it is difficult to etchthe reaction product enough by adjusting the voltage value applied tothe FS electrode 40 during the etching.

Again in the conventional etching apparatus, part of the insulatingmaterial to which the reaction product is not adhered or adhered thinly,e.g., the periphery of the top plate 7, is excessively sputtered due toan excessive voltage component derived from the high frequency voltageapplied to the FS electrode 40 (and caused by the capacitive coupling).This also brings about a problem of significant waste of the insulatingmaterial.

In view of the above, an object of the present invention is to preventthe insulating material forming the chamber inner wall from being etchedand to suppress the particle generation derived from the reactionproduct remaining in the chamber.

To achieve the object, a first plasma etching apparatus according to thepresent invention comprises: a chamber capable of reducing pressure; asubstrate support provided inside the chamber to carry a substrate; afirst electrode arranged outside and in proximity to the chamber, towhich high frequency power is applied to generate plasma comprising anetching gas in the chamber; and a second electrode comprising aplurality of separated electrodes arranged between the chamber and thefirst electrode, to each of which high frequency power is appliedindependently.

In the present invention, high frequency means a frequency not lowerthan 10 kHz and not higher than 10 GHz.

In the first plasma etching apparatus, the second electrode may beprovided within the chamber wall.

In the first plasma etching apparatus, it is preferable that thesubstrate support is arranged such that the surface of the substratecarried thereon is opposed to the second electrode and the secondelectrode comprises the plurality of separated electrodes combinedconcentrically. In this case, the second electrode may comprise theplurality of separated electrodes each having a circular circumference.

A second plasma etching apparatus according to the present inventioncomprises: a chamber capable of reducing pressure; a substrate supportprovided inside the chamber to carry a substrate; a first electrodearranged outside and in proximity to the chamber, to which highfrequency power is applied to generate plasma comprising an etching gasin the chamber; a second electrode arranged between the chamber and thefirst electrode, to which high frequency power is applied; and a drivemechanism for moving the second electrode between the chamber and thefirst electrode along a wall of the chamber.

A third plasma etching apparatus according to the present inventioncomprises: a chamber capable of reducing pressure; a substrate supportprovided inside the chamber to carry a substrate; a first electrodearranged outside and in proximity to the chamber, to which highfrequency power is applied to generate plasma comprising an etching gasin the chamber; a second electrode arranged between the chamber and thefirst electrode, to which high frequency power is applied; a detectionmeans for detecting an etching reaction product adhered to part of aninner wall of the chamber opposing to the second electrode; and a drivemechanism for moving the second electrode between the chamber and thefirst electrode along a wall of the chamber in response to an etchingreaction product detection signal from the detection means.

A first plasma etching process according to the present invention is aplasma etching process using the first plasma etching apparatusaccording to the present invention. Specifically, the process comprisesthe steps of: placing a substrate provided with a film to be etched onthe substrate support; introducing an etching gas in the chamber andapplying high frequency power to the first electrode after the step ofplacing the substrate to generate plasma comprising the etching gas inthe chamber; and etching the film to be etched with the plasma whileapplying high frequency power independently to each of the plurality ofseparated electrodes serving as the second electrode based on athickness distribution of an etching reaction product adhered to part ofan inner wall of the chamber opposing to the second electrode.

A second plasma etching process according to the present invention is aplasma etching process using the first plasma etching apparatusaccording to the present invention. Specifically, the process comprisesthe steps of: placing a substrate provided with a film to be etched onthe substrate support; introducing an etching gas in the chamber andapplying high frequency power to the first electrode after the step ofplacing the substrate to generate plasma comprising the etching gas inthe chamber; etching the film to be etched with the plasma; and applyinghigh frequency power independently to each of the plurality of separatedelectrodes serving as the second electrode based on a thicknessdistribution of an etching reaction product adhered to part of an innerwall of the chamber opposing to the second electrode after the step ofetching the film to be etched.

In the first or second plasma etching process, it is preferable that, inthe step of applying the high frequency power independently to each ofthe plurality of separated electrodes, uniform etching is carried out tothe etching reaction product regardless of the thickness distribution ofthe etching reaction product.

A third plasma etching process according to the present invention is aplasma etching process using the second plasma etching apparatusaccording to the present invention. Specifically, the process comprisesthe steps of: placing a substrate provided with a film to be etched onthe substrate support; introducing an etching gas in the chamber andapplying high frequency power to the first electrode after the step ofplacing the substrate to generate plasma comprising the etching gas inthe chamber; and etching the film to be etched with the plasma andsimultaneously applying high frequency power to the second electrodewhile moving the second electrode along a wall of the chamber using thedrive mechanism based on a thickness distribution of an etching reactionproduct adhered to part of an inner wall of the chamber opposing to thesecond electrode.

A fourth plasma etching process according to the present invention is aplasma etching process using the third plasma etching apparatusaccording to the present invention. Specifically, the process comprisesthe steps of: placing a substrate provided with a film to be etched onthe substrate support; introducing an etching gas in the chamber andapplying high frequency power to the first electrode after the step ofplacing the substrate to generate plasma comprising the etching gas inthe chamber; and etching the film to be etched with the plasma andsimultaneously detecting a thickness distribution of an etching reactionproduct adhered to part of an inner wall of the chamber opposing to thesecond electrode using the detection means and applying high frequencypower to the second electrode while moving the second electrode along awall of the chamber using the drive mechanism based on the detectedthickness distribution.

In the third or fourth plasma etching process, it is preferable that, inthe step of applying the high frequency power to the second electrode,uniform etching is carried out to the etching reaction productregardless of the thickness distribution of the etching reactionproduct.

In the first to fourth plasma etching processes, it is preferable thatthe film to be etched is a film containing at least a noble metalelement or a platinum group element and the etching gas is achlorine-containing gas.

As explained above, according to the present invention, the secondelectrode such as a Faraday shield electrode comprises a plurality ofseparated electrodes and a high frequency voltage is appliedindependently to each of the separated electrodes based on the thicknessdistribution of the reaction product adhered to the chamber inner wall.Or alternatively, with the second electrode being moved along thechamber wall, a high frequency voltage is applied depending on thethickness of the reaction product adhered to a position to which thesecond electrode has been moved. Therefore, the reaction productremaining in the chamber is etched enough while part of the chamberinner wall immediately below the first electrode such as an ICP coil isprevented from being etched. Accordingly, particle generation derivedfrom the reaction product is suppressed while exerting an originalfunction of the second electrode, i.e., the waste of the insulatingmaterial forming the chamber is prevented with reliability. Thereby, theplasma etching of the electrode material film is carried out at lowcosts with fewer defects. In particular, in manufacturing an electrodeof a ferroelectric memory, the present invention shows a remarkableeffect if applied to the etching of a noble metal film or a platinumgroup metal film which gives a reaction product whose boiling point istoo high for easy vaporization, i.e., a reaction product hard to exhaustout of the chamber.

That is, the present invention relates to a plasma etching apparatus anda plasma etching process and is particularly effective if applied to amanufacturing process including patterning of an electrode material filmof a ferroelectric capacitor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a view illustrating a schematic configuration of a plasmaetching apparatus according to a first embodiment of the presentinvention and FIG. 1B is a plan view illustrating a first FS electrodeand a second FS electrode of the etching apparatus shown in FIG. 1A.

FIGS. 2A to 2C are sectional views illustrating the steps ofmanufacturing a capacitive element using a plasma etching processaccording to first and second embodiments of the present invention.

FIG. 3A is a view illustrating a degree of adhesion of a reactionproduct during etching in a conventional plasma etching apparatus andFIG. 3B is a view illustrating a degree of adhesion of a reactionproduct during etching in the plasma etching apparatus according to thefirst embodiment of the present invention.

FIG. 4A is a view illustrating a schematic configuration of a plasmaetching apparatus according to a second embodiment of the presentinvention and FIG. 4B is a plan view illustrating an FS electrode of theetching apparatus shown in FIG. 4A.

FIG. 5A is a view illustrating a schematic configuration of aconventional plasma etching apparatus and FIG. 5B is a plan viewillustrating an FS electrode of the etching apparatus shown in FIG. 5A.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment

Hereinafter, an explanation is given to a plasma etching apparatus and aplasma etching process according to a first embodiment of the presentinvention with reference to the drawings.

FIG. 1A is a view illustrating a schematic configuration of the plasmaetching apparatus according to the first embodiment of the presentinvention. The plasma etching apparatus of the present embodiment allowsgeneration of plasma which couples inductively with an ICP coil andplasma which couples capacitively with an FS electrode. As to bedescribed later, a major feature of the apparatus is that the FSelectrode is separated in two or more.

More specifically, as shown in FIG. 1A, the apparatus of the presentembodiment includes an electrode 2 serving also as a wafer supportarranged in a chamber 1 for performing plasma treatment such as dryetching, i.e., a chamber 1 capable of reducing pressure. The electrode 2is installed on the bottom of the chamber 1 via a support member 2 a.Further, a wafer 3 to be plasma-treated is placed on the electrode 2 anda high frequency bias voltage is applied to the electrode 2 from a highfrequency power source 4.

At the top of the chamber 1, a top plate 7 made of quartz or ceramic isprovided to be opposed to the electrode 2 or the wafer 3. A highfrequency electrode for generating major plasma to etch the wafer 3 inthe chamber 1, i.e., an inductively coupled coil 5, is provided inproximity to the top surface of the top plate 7, i.e., an outer wall ofthe chamber 1. A high frequency voltage (high frequency power) issupplied to the ICP coil 5 from a high frequency power source 6.

A feature of the present embodiment is that two separated electrodes,specifically a first FS electrode 8 and a second FS electrode 9, areinserted between the ICP coil 5 and the top plate 7. The first andsecond FS electrodes 8 and 9 may be spaced from the top plate 7 or incontact with the top plate 7 depending on the material of the top plate7. Further, the first and second FS electrodes 8 and 9 may be buried inthe top plate 7 so as not to appear on the surface of the top plate 7serving as the inner wall surface of the chamber.

During the etching of the wafer 3, a suitably adjusted high frequencyvoltage (high frequency power) is applied independently to the first andsecond FS electrodes 8 and 9 from high frequency power sources 10 and11, respectively. This prevents the insulating material, especiallyforming the top plate 7, from being etched by plasma ion impact.

FIG. 1B is a plan view illustrating the first and second FS electrodes 8and 9 of the etching apparatus shown in FIG. 1A. As shown in FIG. 1B,the first FS electrode 8 is ring-shaped when viewed in plan, while thesecond FS electrode 9 is disc-shaped when viewed in plan. Further, thefirst and second FS electrodes 8 and 9 are combined concentrically.

The etching apparatus shown in FIG. 1A has an exhaust port 13 at thebottom thereof. Releasing a gate valve 12 brings a pressure-reducedstate in the chamber 1.

Hereinafter, a plasma etching process using the plasma etching apparatusof the present embodiment shown in FIG. 1A will be described withreference to the drawings.

FIGS. 2A to 2C are sectional views illustrating the steps ofmanufacturing a capacitive element (memory capacity) of a ferroelectricmemory cell in which a ferroelectric film comprising SBT or PZT is usedas an insulating film for the capacitive element.

First, as shown in FIG. 2A, a SiN film 30 is formed on a semiconductorsubstrate (not shown) by CVD (chemical vapor deposition), for example.Then, a contact hole for connecting a memory capacitive electrode andthe semiconductor substrate is opened in the SiN film 30, in whichtungsten (W) is buried to form a contact plug 31. Then, a layered metalfilm containing a noble metal element or a platinum group element isformed over the contact plug 31 and the SiN film 30. More specifically,an Ir film 32 of 50 nm thickness, an IrO₂ film 33 of 50 nm thickness anda Pt film 34 of 100 nm thickness are deposited in this order. Further, aTiAlN film 35 of 100 nm thickness is deposited on the Pt film 34, whichis then etched using a resist pattern 36 covering an electrode formationarea as a mask. The Ir film 32 of 50 nm thick may be replaced with alayered film of a 100 nm thick TiAlN film and a 50 nm thick Ir film.

After the resist pattern 36 is removed as shown in FIG. 2B, thesemiconductor substrate provided with the above-described layered metalfilm is placed on the electrode 2 in the chamber 1 of the plasma etchingapparatus shown in FIG. 1A. Then, using the patterned TiAlN film 35 as amask, the Pt film 34, IrO₂ film 33 and Ir film 32 are selectively etchedin sequence with a gas mixture of chlorine (Cl₂) and oxygen (O₂). Thus,the Ir film 32, IrO₂ film 33 and Pt film 34 are patterned to form alower capacitive electrode. Specific etching conditions are shown inTable 2. TABLE 2 ICP/RF power 1500 W/200 W, 13.56 MHz FS electrode powerInner electrode: 300 W, 13.56 MHz Outer electrode: 200 W, 12.56 MHzCl₂/O₂ Flow rate 100 ml/min (standard conditions)/ 250 ml/min (standardconditions) Pressure 2.0 Pa Temperature of lower electrode 50° C. Numberof particles increased 0.2 μm or more: 20 particles

As seen in Table 2, high frequency power is supplied independently toeach of the first and second FS electrodes 8 and 9 in the dry etchingstep of the present embodiment. More specifically, high frequency powerof 200 W (at a frequency of 12.56 MHz) is applied to the first FSelectrode 8 (outer electrode) and high frequency power of 300 W (at afrequency of 13.56 MHz) is applied to the second FS electrode 9 (innerelectrode) to perform the etching. In Table 2, the lower electrodecorresponds to the electrode 2 of the plasma etching apparatus shown inFIG. 1A. That is, during the etching, high frequency power of 1500 W (ata frequency of 13.56 MHz) is applied to the ICP coil 5 and highfrequency power of 200 W (at a frequency of 13.56 MHz) is applied to thelower electrode (electrode 2) so as to control energy of ions in theetching gas entering the substrate. Further, as shown in Table 2, Cl₂gas and O₂ gas are introduced at flow rates of 100 ml/min (normal state)and 250 ml/min (normal state), respectively. The pressure in the chamber1 is 2.0 Pa and the temperature of the lower electrode is 50 ° C.

Then, referring to FIG. 2C, the TiAlN film 35 is removed and then aninterlayer insulating film 37 is formed over the whole surface of thesemiconductor substrate to have a flat surface. Then, an opening isformed in the interlayer insulating film 37 to expose the surface of thePt film 34. Subsequently, a ferroelectric film 38 serving as acapacitive insulating film is formed on the Pt film 34 and theinterlayer insulating film 37 by patterning, and then an uppercapacitive electrode 39 made of Pt, for example, is formed to cover theferroelectric film 38.`

According to the above process of manufacturing the memory capacitanceelement, in the step of etching the layered film of the Pt film 34, IrO₂film 33 and Ir film 32 (see FIG. 2B), the high-frequency power isapplied independently to each of the first and second FS electrodes 8and 9. At this time, the power applied to the second FS electrode 9 ishigher than that applied to the first electrode 8. As described above,in the apparatus as shown in FIG. 1A in which the wafer 3 is opposed tothe top plate 7 or the ICP coil 5 outside the top plate 7, the etchingreaction product adheres in larger thickness to the center part of thesurface of the top plate 7 serving as the inner wall surface of thechamber than to the periphery of the top plate 7. However, by applyinghigher power to the second FS electrode 9 than to the first FS electrode8 as in the present embodiment, the etch rate for the reaction productadhered to the center part of the top plate 7 becomes higher than theetch rate for the reaction product adhered to the periphery of the topplate 7. That is, the reaction product is etched uniformly over theentire surface of the top plate 7 by optimizing the power applied to thetwo FS electrodes 8 and 9. Therefore, the reaction product is completelyremoved eventually and the excessive etching of the insulating materialforming the top plate 7 is avoided.

FIGS. 3A and 3B illustrate the state of the surface of the top plate 7serving as the inner wall surface of the chamber and the vicinitythereof during the etching of the above-described electrode materialfilm made of Ir and Pt for forming a ferroelectric memory device, forexample. FIG. 3A shows the state where the conventional plasma etchingapparatus (see FIG. 5A) is used, while FIG. 3B shows the state where theplasma etching apparatus according to the present embodiment (see FIG.1A) is used.

As shown in FIG. 3A, with the conventional apparatus, high frequencypower is applied uniformly to the entire surface of the FS electrode 40,whereby a self-bias potential Vpp takes a uniform value of 200 V.Accordingly, among the Ir- or Pt-containing etching reaction productadhered unevenly to the surface of the top plate 7 due to the relativearrangement of the wafer 3 (not shown) and the top plate 7, the etchingreaction product 41 adhered to the center part of the surface of the topplate 7 cannot be removed.

On the other hand, as shown in FIG. 3B, when the etching apparatus ofthe present embodiment is used, high frequency power is appliedindependently to each of the first and second FS electrodes 8 and 9depending on the thickness of the reaction product adhered to thesurface of the top plate 7. Accordingly, the self-bias potential Vppcaused by the high frequency power is set to 300 V at the center part ofthe top plate 7 and 200 V at the periphery of the top plate 7. Thereby,the etch rate for the reaction product is adjusted depending on wherethe reaction product is adhered such that the reaction product can beremoved uniformly in the same period of time. In other words, theetching reaction product is etched uniformly over the entire surface ofthe top plate 7 regardless of the thickness distribution of the reactionproduct, whereby the reaction product hardly adheres to the top plate 7.

As a result of etching according to the above-described plasma etchingprocess of the present embodiment, the number of particles of 0.2 μmdiameter or more increased on a 8-inch circular wafer was about 20 asshown in Table 2. On the other hand, when the conventional plasmaetching apparatus shown in FIG. 5A was used to carry out the etching byapplying high frequency power to the FS electrode 40, the number ofparticles of 0.2 μm diameter or more increased on a 8-inch circularwafer was about 500. Thus, as compared with the prior art, the presentembodiment allows significant reduction of the number of particlesgenerated.

As described above, according to the present embodiment, the FSelectrodes 8 and 9 are used and high frequency power is appliedindependently to each of the FS electrodes 8 and 9 based on thethickness distribution of the reaction product adhered to the chamberinner wall. As a result, the reaction product remaining in the chamber 1is etched enough while part of the chamber inner wall (top plate 7)immediately below the ICP coil 5 is prevented from being etched.Accordingly, the particle generation derived from the reaction productis suppressed while an original function of the FS electrode is exerted,i.e., the waste of the insulating material forming the chamber 1including the top plate 7 is prevented with reliability. Thus, theplasma etching of the electrode material film can be carried out at lowcosts with fewer defects. In particular, in manufacturing an electrodeof a ferroelectric memory, the present embodiment shows a remarkableeffect if applied to the etching of a noble metal film or a platinumgroup metal film which gives a reaction product whose boiling point istoo high for easy vaporization, i.e., a reaction product hard to exhaustout of the chamber.

In the present embodiment, the ring-shaped first FS electrode 8 and thedisc-shaped second FS electrode 9 are used in combination, but it goeswithout saying that the number and shape of the FS electrode are notparticularly limited. However, if the surface of the substrate placed onthe substrate support (electrode 2) is arranged to be opposed to the FSelectrode as in the present embodiment, it is preferred to use aplurality of concentrically combinable FS electrodes, especially thosehaving circular circumferences, respectively. With this arrangement, thehigh frequency power can easily be applied independently to each of theFS electrodes based on the thickness distribution of the reactionproduct adhered to the chamber inner wall.

In the present embodiment, a detection means may be provided fordetecting the etching reaction product adhered to the surface of the topplate 7 serving as the inner wall surface of the chamber (e.g., aphotodetector 24 according to a second embodiment).

Further, in the present embodiment, the electrode material film isetched while the high frequency power is applied to each of the firstand second FS electrodes 8 and 9 to remove the reaction product.However, as an alternative to this process, the layered electrodematerial film may be first etched as shown in FIG. 2B, and the highfrequency power may be then applied independently to each of the firstand second FS electrodes 8 and 9 to remove the reaction productgenerated through the etching while the semiconductor substrate providedwith the layered electrode material film is mounted on the electrode 2in the chamber 1 of the etching apparatus shown in FIG. 1A or after itis taken out of the chamber 1. Also in this case, the step following theremoval of the reaction product is the same as that explained withreference to FIG. 2C.

Second Embodiment

Hereinafter, an explanation is given to a plasma etching apparatus and aplasma etching process according to a second embodiment of the presentinvention with reference to the drawings.

FIG. 4A is a view illustrating a schematic configuration of a plasmaetching apparatus according to the second embodiment of the presentinvention. The plasma etching apparatus of the present embodiment allowsgeneration of plasma which couples inductively with an ICP coil andplasma which couples capacitively with an FS electrode. Major featuresthereof are that the FS electrode moves in a creeping manner along a topplate at the top of a chamber 1 and that a device for monitoring in-situa deposit adhered to the top plate (etching reaction product) isprovided. That is, according to the etching process of the presentinvention, the etching is carried out while the step is repeated ofspecifying a position on the top plate where the reaction product isadhered by the in-situ monitoring and moving the FS electrode to theposition to remove the reaction product.

More specifically, as shown in FIG. 4A, the apparatus of the presentembodiment includes an electrode 2 serving also as a wafer supportarranged in a chamber 1 for performing plasma treatment such as dryetching, i.e., a chamber 1 capable of reducing pressure. The electrode 2is installed on the bottom of the chamber 1 via a support member 2 a.Further, a wafer 3 to be plasma-treated is placed on the electrode 2 anda high frequency bias voltage is applied to the electrode 2 from a highfrequency power source 4.

At the top of the chamber 1, a top plate 7 made of quartz or ceramic isprovided to be opposed to the electrode 2 or the wafer 3. A highfrequency electrode for generating major plasma in the chamber 1 to etchthe wafer 3, i.e., an ICP coil 5, is provided in proximity to the topsurface of the top plate 7, i.e., an outer wall of the chamber 1. A highfrequency voltage (high frequency power) is supplied to the ICP coil 5from a high frequency power source 6.

An FS electrode 20 is inserted between the ICP coil 5 and the top plate7. The FS electrode 20 may be spaced from the top plate 7 or in contactwith the top plate 7 depending on the material of the top plate 7.

During the etching of the wafer 3, a suitably adjusted high frequencyvoltage (high frequency power) is applied to the FS electrode 20 from ahigh frequency power source 21, which prevents the insulating material,especially forming the top plate 7, from being etched by plasma ionimpact and removes the reaction product adhered to the surface of thetop plate 7 serving as the inner wall surface of the chamber 1.

A first feature of the apparatus of the present embodiment is that theapparatus includes a drive unit 23 for moving the FS electrode 20between the top plate 7 and the ICP coil 5 along the surface of the topplate 7. The drive unit 23 is connected to the FS electrode 20 via anarm 22 operatively connected with the drive unit 23.

FIG. 4B is a plan view of the FS electrode 20 of the etching apparatusshown in FIG. 4A. As shown in FIG. 4B, the FS electrode 20 isdisc-shaped when viewed in plan. In general, the FS electrode 20 ispreferably in such a shape.

A second feature of the apparatus of the present embodiment is that theapparatus includes, on the side of the chamber 1, a detection means fordetecting the etching reaction product adhered to the surface of the topplate 7 serving as the inner wall surface of the chamber, to be morespecific, a photodetector 24. Though not shown, an optical sensor devicesuch as a CCD (charge-coupled device) is mounted to the tip of thephotodetector 24. When the reaction product is adhered to the surface ofthe top plate 7 during the etching, the optical sensor device reads aperiodical change over time of interference light 25 caused by aninterference phenomenon of lights reflected from the upper and lowersurfaces of a film of the adhered reaction product (change in filminterference signal), with light emitted by the plasma as a lightsource. Thereby, the degree of growth of the adhered film is detected.Further, since the photodetector 24 is operatively connected with thedrive unit 23, the film interference signal detected by thephotodetector 24 is fed back to the drive unit 23 to move the FSelectrode 20 appropriately. More specifically, the angle of thephotodetector 24 (direction for measuring the interference light 25) ischanged over time during the etching to scan the whole surface of thetop plate 7 and the growth of the adhered film is monitored based on thethus obtained periodical change in the interference light 25. Then,based on the change in the interference light 25 detected by thephotodetector 24, the drive unit 23 moves the FS electrode 20 via thearm 22 to a position where the adhered film has grown large. Thus, theadhered film in that position, i.e., the reaction product, is removed.

The etching apparatus shown in FIG. 4A has an exhaust port 13 at thebottom thereof. Releasing a gate valve 12 brings a pressure-reducedstate in the chamber 1.

The steps of manufacturing a capacitive element (memory capacity) of aferroelectric memory cell which employs a ferroelectric film made of SBTor PZT as an insulating film for the capacitive element using the plasmaetching apparatus of the present embodiment shown in FIG. 4A arebasically the same as those of the first embodiment shown in FIGS. 2A to2C. However, in detail, the step corresponding to the step shown in FIG.2B is different.

More specifically, in the present embodiment, the same step as that ofthe first embodiment shown in FIG. 2A is carried out, and then in thestep shown in FIG. 2B, the Pt film 34, IrO₂ film 33 and Ir film 32 areetched in sequence under different etching conditions from those of thefirst embodiment to form a lower capacitive electrode. Specific etchingconditions are shown in Table 3. TABLE 3 ICP/RF power 1500 W/200 W,13.56 MHz FS electrode power 500 W, 12.56 MHz Cl₂/O₂ Flow rate 100ml/min (standard conditions)/ 250 ml/min (standard conditions) Pressure2.0 Pa Temperature of lower electrode 50° C. Number of particlesincreased 0.2 μm or more: 20 particles

As shown in Table 3, in the dry etching process according to the presentembodiment, high frequency power of 500 W (at a frequency of 12.56 MHz)is applied to the FS electrode 20 to perform the etching. In Table 3,the lower electrode corresponds to the electrode 2 of the plasma etchingapparatus shown in FIG. 4A. That is, during the etching, high frequencypower of 1500 W (at a frequency of 13.56 MHz) is applied to the ICP coil5 and high frequency power of 200 W (at a frequency of 13.56 MHz) isapplied to the lower electrode (electrode 2) so as to control energy ofions in the etching gas entering the substrate. Further, as seen inTable 3, Cl₂ gas and O₂ gas are introduced at flow rates of 100 ml/min(normal state) and 250 ml/min (normal state), respectively. The pressurein the chamber 1 is 2.0 Pa and the temperature of the lower electrode is50° C.

More specifically, in the dry etching process of the present embodiment,the ICP coil 5 and the electrode 2 are applied with the high frequencypower, respectively, to generate plasma. In addition, while a certainhigh frequency power is being applied to the FS electrode 20, the wholesurface of the top plate 7 is scanned by the photodetector 24 to detectthickness distribution of the reaction product containing Pt or Ir. Theetching process may be carried out while the FS electrode 20 is moved toa position where the reaction product has grown relatively large basedon the detection result to effectively remove the reaction product inthat position. Or alternatively, the etching process may be carried outwhile the high frequency power applied to the FS electrode 20 is varieddepending on the thickness of the reaction product adhered to theposition where the FS electrode 20 has been moved to (more specifically,the high frequency power applied is increased as the thickness of thereaction product becomes larger). In any case, the etching reactionproduct is etched uniformly over the whole surface of the top plate 7regardless of the thickness distribution thereof. Thus, the reactionproduct hardly adheres to the top plate 7.

The step following to the above-described etching step is the same asthe step of the first embodiment shown in FIG. 2C.

The above explanation is based on the premise that a singlephotodetector 24 is used. However, two or more photodetectors 24 may beused to divide the range of detection of the interference light 25 bythe photodetectors 24 into the center part and the periphery of the topplate 7, for example. If such division is made, the degree of growth ofthe adhered reaction product film is detected with more efficiency,which allows more efficient removal.

As described above, according to the present embodiment, the in-situmonitoring is carried out using the photodetector 24 during the etchingof the layered film containing Ir or Pt to specify a position on the topplate 7 where the deposit (etching reaction product) is adhered, andthen the FS electrode 20 is moved to the specified position as needed toremove the deposit. Thus, the etching of the layered film is carried outwhile the removal of the deposit is repeated. That is, since the etchingof the reaction product by the FS electrode 20 is carried out only onthe position of the top plate 7 where the reaction product is adhered,the reaction product, which is adhered unevenly, is completely etchedaway while the waste of part of the insulting material forming the topplate 7 or the chamber 1 to which the reaction product is not adhered isprevented. Thus, the particle generation derived from the reactionproduct is suppressed while an original function of the FS electrode 20is exerted, i.e., the waste of the insulating material forming thechamber 1 including the top plate 7 is prevented with reliability.Thereby, the plasma etching of the electrode material film is carriedout at low costs with fewer defects. In particular, in manufacturing anelectrode of a ferroelectric memory, the present embodiment shows aremarkable effect if applied to the etching of a noble metal film or aplatinum group metal film which gives a reaction product whose boilingpoint is too high for easy vaporization, i.e., a reaction product hardto exhaust out of the chamber.

As a result of etching according to the above-described plasma etchingprocess of the present embodiment, the number of particles of 0.2 μmdiameter or more increased on a 8-inch circular wafer was about 20 asshown in Table 3. On the other hand, when the conventional plasmaetching apparatus shown in FIG. 5A was used to carry out the etching byapplying the high frequency voltage to the FS electrode 40, the numberof particles of 0.2 μm diameter or more increased on a 8-inch circularwafer was about 500. Thus, as compared with the prior art, the presentembodiment allows significant reduction of the number of particlesgenerated.

In the second embodiment, the reaction product is removed simultaneouslywith the etching of the electrode material film by moving the FSelectrode 20 and applying high frequency power thereto. However,alternatively, the layered electrode material film may be first etchedas shown in FIG. 2B, and the removal of the reaction product generatedduring the etching may be then carried out by moving the FS electrode 20and applying high frequency power to the FS electrode 20, while thesemiconductor substrate provided with the layered electrode materialfilm is mounted on the electrode 2 in the chamber 1 of the etchingapparatus shown in FIG. 4A or after it is taken out of the chamber 1.Also in this case, the step following the removal step of the reactionproduct is the same as the step shown in FIG. 2C.

Further, in the second embodiment, the photodetector 24 is provided as adetection means for detecting the etching reaction product adhered tothe surface of the top plate 7 serving as the inner wall surface of thechamber. However, it is needless to say that the detection means is notlimited to the photodetector 24. Further, the thickness distribution ofthe etching reaction product may be obtained without using the detectionmeans such as the photodetector 24.

In the first and second embodiments, it goes without saying that thefilm to be etched is not limited to the film containing a noble metalelement or a platinum group element. That is, in the first and secondembodiments, an object to be etched is an electrode material film whichgives the etching reaction product whose boiling point is too high foreasy vaporization (i.e., which remains easily). However, it is needlessto say that the same effect is obtained if a material film used in othersemiconductor manufacturing processes or material production process istargeted. Likewise, the kind of etching gas used in the first and secondembodiments is not particularly limited to the gas mixture of Cl₂ gasand O₂ gas and other chlorine-containing gas may be used.

In the first and second embodiments, targeted is an etching apparatusincluding the ICP coil and the FS electrode (inductively coupled plasmaetching apparatus), but the present invention is not limited thereto.The present invention can be applied to any etching apparatus includinga first electrode provided outside the chamber and applied with highfrequency power for generating plasma in the chamber and a secondelectrode provided between the chamber and the first electrode andapplied with high frequency power.

1. A plasma etching apparatus comprising: a chamber capable of reducingpressure; a substrate support provided inside the chamber to place asubstrate; a first electrode which is arranged outside and in proximityto the chamber and to which high frequency power is applied to generateplasma of an etching gas in the chamber; and a second electrodecomprising a plurality of separated electrodes which are arrangedbetween the chamber and the first electrode and to each of which highfrequency power is applied independently.
 2. A plasma etching apparatusaccording to claim 1, wherein the substrate support is arranged suchthat the surface of the substrate placed thereon is opposed to thesecond electrode, and the second electrode comprises the plurality ofseparated electrodes combined concentrically.
 3. A plasma etchingapparatus according to claim 2, wherein the second electrode comprisesthe plurality of separated electrodes each having a circularcircumference.
 4. A plasma etching apparatus comprising: a chambercapable of reducing pressure; a substrate support provided inside thechamber to place a substrate; a first electrode which is arrangedoutside and in proximity to the chamber and to which high frequencypower is applied to generate plasma of an etching gas in the chamber; asecond electrode which is arranged between the chamber and the firstelectrode and to which high frequency power is applied; and a drivemechanism for moving the second electrode between the chamber and thefirst electrode along a wall of the chamber.
 5. A plasma etchingapparatus comprising: a chamber capable of reducing pressure; asubstrate support provided inside the chamber to place a substrate; afirst electrode which is arranged outside and in proximity to thechamber and to which high frequency power is applied to generate plasmaof an etching gas in the chamber; a second electrode which is arrangedbetween the chamber and the first electrode and to which high frequencypower is applied; a detection means for detecting an etching reactionproduct adhered to part of an inner wall of the chamber opposing to thesecond electrode; and a drive mechanism for moving the second electrodebetween the chamber and the first electrode along a wall of the chamberin response to an etching reaction product detection signal from thedetection means. 6-17. (canceled)